Effects of Different Biochar Amendments on Soil Enzyme Activities and Carbondioxide Emission

Biochar production from organic waste offers an important alternative for waste management, also improves soil properties (bio-physico-chemical) and reduces heavy metal pollution risk caused by the excessive use of chemical fertilizers applied directly to the soils. Biochar is also proposed as an important management strategy to mitigate the negative impacts of greenhouse gases, which are among the most important causes of global climate change. This study aimed to investigate the effects of biochars produced from six different plant wastes on soil enzyme activity, CO2–C emission, total nitrogen (Nt), and nitrate (NO3–N) concentrations. Almond shell (AS), tobacco waste (TW), pomegranate peel (PP), cotton waste (CW), orange peel (OP), and wheat straw (WS) biochars were applied to the soil at the rates of 0.5, 1.0, and 1.5%, and the biochar amended soils were incubated in the laboratory environment (25 ± 2) for 37 weeks. The highest CO2 ̶ C emission was recorded in OP biochar treatment, while the lowest emission was measured in PP treatment, indicating that OP biochar addition tended to decrease C mineralization in the soil. The addition of AS biochar significantly increased the dehydrogenase and urease enzyme activities, while urease activity did not show a significant increase. The results can be attributed to the differences in composition and properties (C: N ratio, pH) of the biochars applied as well as the nature of the feedstocks used in biochar production. Biochar applications increased the Nt and NO3–N concentrations of the soils, and the highest increase was obtained in the WS treatment. The results of the study revealed that PP biochar can be recommended to reduce CO2–C emission from soils, AS biochar has a significant effect on urease and dehydrogenase enzyme activities, and the effect of WS biochar on Nt and NO3–N concentrations of soils were higher than the other five biochar types.